/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * drivers/pwm.c
 *
 *   Copyright (C) 2011-2013, 2016 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Compilation Switches
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <semaphore.h>
#include <fcntl.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <tinyara/arch.h>
#include <tinyara/kmalloc.h>
#include <tinyara/semaphore.h>
#include <tinyara/fs/fs.h>
#include <tinyara/pwm.h>

#include <arch/irq.h>

#ifdef CONFIG_PWM

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/
/* Debug ********************************************************************/
/* Non-standard debug that may be enabled just for testing PWM */

#define PWM_PREVENT_MULTIPLE_OPEN   0

#ifdef CONFIG_DEBUG_PWM_INFO
#define pwmdbg    dbg
#define pwmvdbg   vdbg
#define pwmlldbg  lldbg
#define pwmllvdbg llvdbg
#else
#define pwmdbg(...)
#define pwmvdbg(...)
#define pwmlldbg(...)
#define pwmllvdbg(...)
#endif

/****************************************************************************
 * Private Type Definitions
 ****************************************************************************/

/* This structure describes the state of the upper half driver */

struct pwm_upperhalf_s {
	uint8_t crefs;				/* The number of times the device has been opened */
	volatile bool started;		/* True: pulsed output is being generated */
#ifdef CONFIG_PWM_PULSECOUNT
	volatile bool waiting;		/* True: Caller is waiting for the pulse count to expire */
#endif
	sem_t exclsem;				/* Supports mutual exclusion */
#ifdef CONFIG_PWM_PULSECOUNT
	sem_t waitsem;				/* Used to wait for the pulse count to expire */
#endif
	struct pwm_info_s info;		/* Pulsed output characteristics */
	FAR struct pwm_lowerhalf_s *dev;	/* lower-half state */
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

static int pwm_open(FAR struct file *filep);
static int pwm_close(FAR struct file *filep);
static ssize_t pwm_read(FAR struct file *filep, FAR char *buffer, size_t buflen);
static ssize_t pwm_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
static int pwm_start(FAR struct pwm_upperhalf_s *upper, unsigned int oflags);
static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg);

/****************************************************************************
 * Private Data
 ****************************************************************************/

static const struct file_operations g_pwmops = {
	pwm_open,					/* open */
	pwm_close,					/* close */
	pwm_read,					/* read */
	pwm_write,					/* write */
	0,							/* seek */
	pwm_ioctl					/* ioctl */
#ifndef CONFIG_DISABLE_POLL
	, 0						/* poll */
#endif
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pwm_open
 *
 * Description:
 *   This function is called whenever the PWM device is opened.
 *
 ****************************************************************************/

static int pwm_open(FAR struct file *filep)
{
	FAR struct inode *inode = filep->f_inode;
	FAR struct pwm_upperhalf_s *upper = inode->i_private;
	uint8_t tmp;
	int ret;

	pwmvdbg("crefs: %d\n", upper->crefs);

	/* Get exclusive access to the device structures */

	ret = sem_wait(&upper->exclsem);
	if (ret < 0) {
		ret = -get_errno();
		goto errout;
	}

	/* Increment the count of references to the device.  If this the first
	 * time that the driver has been opened for this device, then initialize
	 * the device.
	 */

	tmp = upper->crefs + 1;
	if (tmp == 0) {
		/* More than 255 opens; uint8_t overflows to zero */

		ret = -EMFILE;
		goto errout_with_sem;
	}

	/* Check if this is the first time that the driver has been opened. */

	if (tmp == 1) {
		FAR struct pwm_lowerhalf_s *lower = upper->dev;

		/* Yes.. perform one time hardware initialization. */

		DEBUGASSERT(lower->ops->setup != NULL);
		pwmvdbg("calling setup\n");

		ret = lower->ops->setup(lower);
		if (ret < 0) {
			goto errout_with_sem;
		}
	}
#if PWM_PREVENT_MULTIPLE_OPEN == 1
	else if (tmp > 1) {
		ret = -EBUSY;
		goto errout_with_sem;
	}
#endif

	/* Save the new open count on success */

	upper->crefs = tmp;
	ret = OK;

errout_with_sem:
	sem_post(&upper->exclsem);

errout:
	return ret;
}

/****************************************************************************
 * Name: pwm_close
 *
 * Description:
 *   This function is called when the PWM device is closed.
 *
 ****************************************************************************/

static int pwm_close(FAR struct file *filep)
{
	FAR struct inode *inode = filep->f_inode;
	FAR struct pwm_upperhalf_s *upper = inode->i_private;
	int ret;

	pwmvdbg("crefs: %d\n", upper->crefs);

	/* Get exclusive access to the device structures */

	ret = sem_wait(&upper->exclsem);
	if (ret < 0) {
		ret = -get_errno();
		goto errout;
	}

	/* Decrement the references to the driver.  If the reference count will
	 * decrement to 0, then uninitialize the driver.
	 */

	if (upper->crefs > 1) {
		upper->crefs--;
	} else {
		FAR struct pwm_lowerhalf_s *lower = upper->dev;

		/* There are no more references to the port */

		upper->crefs = 0;

		/* Disable the PWM device */

		DEBUGASSERT(lower->ops->shutdown != NULL);
		pwmvdbg("calling shutdown: %d\n");

		lower->ops->shutdown(lower);
	}
	ret = OK;

//errout_with_sem:
	sem_post(&upper->exclsem);

errout:
	return ret;
}

/****************************************************************************
 * Name: pwm_read
 *
 * Description:
 *   A dummy read method.  This is provided only to satisfy the VFS layer.
 *
 ****************************************************************************/

static ssize_t pwm_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
{
	/* Return zero -- usually meaning end-of-file */

	return 0;
}

/****************************************************************************
 * Name: pwm_write
 *
 * Description:
 *   A dummy write method.  This is provided only to satisfy the VFS layer.
 *
 ****************************************************************************/

static ssize_t pwm_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
{
	return 0;
}

/****************************************************************************
 * Name: pwm_start
 *
 * Description:
 *   Handle the PWMIOC_START ioctl command
 *
 ****************************************************************************/

#ifdef CONFIG_PWM_PULSECOUNT
static int pwm_start(FAR struct pwm_upperhalf_s *upper, unsigned int oflags)
{
	FAR struct pwm_lowerhalf_s *lower = upper->dev;
	irqstate_t flags;
	int ret = OK;

	DEBUGASSERT(upper != NULL && lower->ops->start != NULL);

	/* Verify that the PWM is not already running */

	if (!upper->started) {
		/* Disable interrupts to avoid race conditions */

		flags = enter_critical_section();

		/* Indicate that if will be waiting for the pulse count to complete.
		 * Note that we will only wait if a non-zero pulse count is specified
		 * and if the PWM driver was opened in normal, blocking mode.  Also
		 * assume for now that the pulse train will be successfully started.
		 *
		 * We do these things before starting the PWM to avoid race conditions.
		 */

		upper->waiting = (upper->info.count > 0) && ((oflags & O_NONBLOCK) == 0);
		upper->started = true;

		/* Invoke the bottom half method to start the pulse train */

		ret = lower->ops->start(lower, &upper->info, upper);

		/* A return value of zero means that the pulse train was started
		 * successfully.
		 */

		if (ret == OK) {
			/* Should we wait for the pulse output to complete?  Loop in
			 * in case the wakeup form sem_wait() is a false alarm.
			 */

			while (upper->waiting) {
				/* Wait until we are awakened by pwm_expired().  When
				 * pwm_expired is called, it will post the waitsem and
				 * clear the waiting flag.
				 */

				int tmp = sem_wait(&upper->waitsem);
				DEBUGASSERT(tmp == OK || get_errno() == EINTR);
			}
		} else {
			/* Looks like we won't be waiting after all */

			pwmvdbg("start failed: %d\n", ret);
			upper->started = false;
			upper->waiting = false;
		}

		leave_critical_section(flags);
	}

	return ret;
}
#else
static int pwm_start(FAR struct pwm_upperhalf_s *upper, unsigned int oflags)
{
	FAR struct pwm_lowerhalf_s *lower = upper->dev;
	int ret = OK;

	DEBUGASSERT(upper != NULL && lower->ops->start != NULL);

	/* Verify that the PWM is not already running */

	if (!upper->started) {
		/* Invoke the bottom half method to start the pulse train */

		ret = lower->ops->start(lower, &upper->info);

		/* A return value of zero means that the pulse train was started
		 * successfully.
		 */

		if (ret == OK) {
			/* Indicate that the pulse train has started */

			upper->started = true;
		}
	}

	return ret;
}
#endif

/****************************************************************************
 * Name: pwm_ioctl
 *
 * Description:
 *   The standard ioctl method.  This is where ALL of the PWM work is done.
 *
 ****************************************************************************/

static int pwm_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
	FAR struct inode *inode = filep->f_inode;
	FAR struct pwm_upperhalf_s *upper = inode->i_private;
	FAR struct pwm_lowerhalf_s *lower = upper->dev;
	int ret;

	pwmvdbg("cmd: %d arg: %ld\n", cmd, arg);

	/* Get exclusive access to the device structures */

	ret = sem_wait(&upper->exclsem);
	if (ret < 0) {
		return ret;
	}

	/* Handle built-in ioctl commands */

	switch (cmd) {
	/* PWMIOC_SETCHARACTERISTICS - Set the characteristics of the next pulsed
	 *   output.  This command will neither start nor stop the pulsed output.
	 *   It will either setup the configuration that will be used when the
	 *   output is started; or it will change the characteristics of the pulsed
	 *   output on the fly if the timer is already started.
	 *
	 *   ioctl argument:  A read-only reference to struct pwm_info_s that provides
	 *   the characteristics of the pulsed output.
	 */

	case PWMIOC_SETCHARACTERISTICS: {
		FAR const struct pwm_info_s *info = (FAR const struct pwm_info_s *)((uintptr_t)arg);
		DEBUGASSERT(info != NULL && lower->ops->start != NULL);

#ifdef CONFIG_PWM_PULSECOUNT
		pwmvdbg("PWMIOC_SETCHARACTERISTICS frequency: %d duty: %08x count: %d started: %d\n", info->frequency, info->duty, info->count, upper->started);
#else
		pwmvdbg("PWMIOC_SETCHARACTERISTICS frequency: %d duty: %08x started: %d\n", info->frequency, info->duty, upper->started);
#endif

		/* Save the pulse train characteristics */

		memcpy(&upper->info, info, sizeof(struct pwm_info_s));

		/* If PWM is already running, then re-start it with the new characteristics */

		if (upper->started) {
#ifdef CONFIG_PWM_PULSECOUNT
			ret = lower->ops->start(lower, &upper->info, upper);
#else
			ret = lower->ops->start(lower, &upper->info);
#endif
		}
	}
	break;

	/* PWMIOC_GETCHARACTERISTICS - Get the currently selected characteristics of
	 *   the pulsed output (independent of whether the output is start or stopped).
	 *
	 *   ioctl argument:  A reference to struct pwm_info_s to receive the
	 *   characteristics of the pulsed output.
	 */

	case PWMIOC_GETCHARACTERISTICS: {
		FAR struct pwm_info_s *info = (FAR struct pwm_info_s *)((uintptr_t)arg);
		DEBUGASSERT(info != NULL);

		memcpy(info, &upper->info, sizeof(struct pwm_info_s));

#ifdef CONFIG_PWM_PULSECOUNT
		pwmvdbg("PWMIOC_GETCHARACTERISTICS frequency: %d duty: %08x count: %d\n", info->frequency, info->duty, info->count);
#else
		pwmvdbg("PWMIOC_GETCHARACTERISTICS frequency: %d duty: %08x\n", info->frequency, info->duty);
#endif
	}
	break;

	/* PWMIOC_START - Start the pulsed output.  The PWMIOC_SETCHARACTERISTICS
	 *   command must have previously been sent.
	 *
	 *   ioctl argument:  None
	 */

	case PWMIOC_START: {
#ifdef CONFIG_PWM_PULSECOUNT
		pwmvdbg("PWMIOC_START frequency: %d duty: %08x count: %d started: %d\n", upper->info.frequency, upper->info.duty, upper->info.count, upper->started);
#else
		pwmvdbg("PWMIOC_START frequency: %d duty: %08x started: %d\n", upper->info.frequency, upper->info.duty, upper->started);
#endif
		DEBUGASSERT(lower->ops->start != NULL);

		/* Start the pulse train */

		ret = pwm_start(upper, filep->f_oflags);
	}
	break;

	/* PWMIOC_STOP - Stop the pulsed output.
	 *
	 *   ioctl argument:  None
	 */

	case PWMIOC_STOP: {
		pwmvdbg("PWMIOC_STOP: started: %d\n", upper->started);
		DEBUGASSERT(lower->ops->stop != NULL);

		if (upper->started) {
			ret = lower->ops->stop(lower);
			upper->started = false;
#ifdef CONFIG_PWM_PULSECOUNT
			if (upper->waiting) {
				upper->waiting = FALSE;
			}
#endif
		}
	}
	break;

	/* Any unrecognized IOCTL commands might be platform-specific ioctl commands */

	default: {
		pwmvdbg("Forwarding unrecognized cmd: %d arg: %ld\n", cmd, arg);
		DEBUGASSERT(lower->ops->ioctl != NULL);
		ret = lower->ops->ioctl(lower, cmd, arg);
	}
	break;
	}

	sem_post(&upper->exclsem);
	return ret;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pwm_register
 *
 * Description:
 *   This function binds an instance of a "lower half" timer driver with the
 *   "upper half" PWM device and registers that device so that can be used
 *   by application code.
 *
 *   When this function is called, the "lower half" driver should be in the
 *   reset state (as if the shutdown() method had already been called).
 *
 * Input parameters:
 *   path - The full path to the driver to be registered in the TinyAra pseudo-
 *     filesystem.  The recommended convention is to name all PWM drivers
 *     as "/dev/pwm0", "/dev/pwm1", etc.  where the driver path differs only
 *     in the "minor" number at the end of the device name.
 *   dev - A pointer to an instance of lower half timer driver.  This instance
 *     is bound to the PWM driver and must persists as long as the driver
 *     persists.
 *
 * Returned Value:
 *   Zero on success; a negated errno value on failure.
 *
 ****************************************************************************/

int pwm_register(FAR const char *path, FAR struct pwm_lowerhalf_s *dev)
{
	FAR struct pwm_upperhalf_s *upper;

	/* Allocate the upper-half data structure */

	upper = (FAR struct pwm_upperhalf_s *)kmm_zalloc(sizeof(struct pwm_upperhalf_s));
	if (!upper) {
		pwmdbg("Allocation failed\n");
		return -ENOMEM;
	}

	/* Initialize the PWM device structure (it was already zeroed by kmm_zalloc()) */

	sem_init(&upper->exclsem, 0, 1);
#ifdef CONFIG_PWM_PULSECOUNT
	sem_init(&upper->waitsem, 0, 0);

	/*
	 * The wait semaphore is used for signaling and, hence, should not
	 * have priority inheritance enabled.
	 */
	sem_setprotocol(&upper->waitsem, SEM_PRIO_NONE);
#endif

	upper->dev = dev;

	/* Register the PWM device */

	pwmvdbg("Registering %s\n", path);
	return register_driver(path, &g_pwmops, 0666, upper);
}

/****************************************************************************
 * Name: pwm_expired
 *
 * Description:
 *   If CONFIG_PWM_PULSECOUNT is defined and the pulse count was configured
 *   to a non-zero value, then the "upper half" driver will wait for the
 *   pulse count to expire.  The sequence of expected events is as follows:
 *
 *   1. The upper half driver calls the start method, providing the lower
 *      half driver with the pulse train characteristics.  If a fixed
 *      number of pulses is required, the 'count' value will be nonzero.
 *   2. The lower half driver's start() methoc must verify that it can
 *      support the request pulse train (frequency, duty, AND pulse count).
 *      If it cannot, it should return an error.  If the pulse count is
 *      non-zero, it should set up the hardware for that number of pulses
 *      and return success.  NOTE:  That is CONFIG_PWM_PULSECOUNT is
 *      defined, the start() method receives an additional parameter
 *      that must be used in this callback.
 *   3. When the start() method returns success, the upper half driver
 *      will "sleep" until the pwm_expired method is called.
 *   4. When the lower half detects that the pulse count has expired
 *      (probably through an interrupt), it must call the pwm_expired
 *      interface using the handle that was previously passed to the
 *      start() method
 *
 * Input parameters:
 *   handle - This is the handle that was provided to the lower-half
 *     start() method.
 *
 * Returned Value:
 *   None
 *
 * Assumptions:
 *   This function may be called from an interrupt handler.
 *
 ****************************************************************************/

#ifdef CONFIG_PWM_PULSECOUNT
void pwm_expired(FAR void *handle)
{
	FAR struct pwm_upperhalf_s *upper = (FAR struct pwm_upperhalf_s *)handle;

	pwmllvdbg("started: %d waiting: %d\n", upper->started, upper->waiting);

	/* Make sure that the PWM is started */

	if (upper->started) {
		/* Is there a thread waiting for the pulse train to complete? */

		if (upper->waiting) {
			/* Yes.. clear the waiting flag and awakened the waiting thread */

			upper->waiting = false;
			sem_post(&upper->waitsem);
		}

		/* The PWM is now stopped */

		upper->started = false;
	}
}
#endif

#endif /* CONFIG_PWM */
